The present invention relates to a vapor-liquid contactor adapted to perform a vapor-liquid contact to thereafter separate gas mixture under a cryogenic distillation, and more particularly to a vapor-liquid contactor for use in the cryogenic air separation unit for carrying out a cryogenic separation of nitrogen, oxygen, argon from air, to a cryogenic air separation unit using the vapor-liquid contactor, and to a method of gas separation using the vapor-liquid contactor.
A distillation column used in a cryogenic air separation unit, etc. includes a packed column, a sieve tray column and the like. Among them, a packed column has an advantage of a low pressure loss (pressure drop) and a low operation cost with comparison to a sieve tray column. Further, the packed column has several advantages in that it can increase a relative volatility between each components of air by setting a low operation pressure according to its low pressure loss; the length of the column can be extended; and thus a high purity of product, especially high purity of argon, can be prepared.
In general, the packed column includes a vapor-liquid contact part formed of a packing, a liquid distributor and the like inside of the column. Such type of structured material is referred to as a vapor-liquid contactor in the present specification.
A structured packing of a self-promoting-fluid-dispersion type is widely used as packing used in the above vapor-liquid contactor.
The self-promoting-fluid-dispersion type structured packing may be provided by processing a metal sheet made of aluminum and the like to an appropriate flexural finishing, laminating and arranging the sheets in a condition of at least one portion thereof to be inclined from the perpendicular axis to disperse the liquid while flowing in a surface of the packing at an angle to the perpendicular axis. Further, it may promote a dispersion of the liquid by providing corrugations and/or unevennesses and/or holes on the surface of the metal sheet. Structured packing is said also regular packing.
Specific examples of the self-promoting-fluid-dispersion type structured packing may include self-promoting-fluid-dispersion type structured packings 71, 81 as shown in FIGS. 6 and 7. FIG. 6 is what is disclosed in Japanese Patent Publication No. (Sho) 57-36009 and FIG. 7 is what is disclosed in Japanese Laid-open Patent No. (Sho) 54-16761. In addition, the self-promoting-fluid-dispersion type structured packing is disclosed in Japanese Patent Publication No. (Hei) 7-113514.
The packing disclosed in Japanese Laid-open Patent No. (Sho) 50-11001 belongs to a scope of the above-mentioned self-promoting-fluid dispersion type structured packing. Such packing is shown in FIG. 8 through FIG. 10. The packing is made of a plurality of thin sheet lattices a, b, c, . . . ; each of the lattices a, b, c, . . . being flexed in a substantially zig-zag pattern and formed of thin sheet strips 13xe2x80x2xcx9c17xe2x80x2 which is inclined to the lattice sections A, B, C, . . . ; and these thin sheet strips 13xe2x80x2xcx9c17xe2x80x2 are integrated with a flexural section 18xe2x80x2 to which a planner cross section of the lattice is formed.
In order to prepare such a packing, band 28xe2x80x2 made of metal thin-sheet is cut in a parallel strip 30xe2x80x2 connected with a plurality of sections 29xe2x80x2. In this case, the cut-out line portion 31xe2x80x2 connected with an adjacent strip 30xe2x80x2 has the same length and only half the length is shift with respect to the adjacent cut line portion 31xe2x80x2. Thereafter, the strip 31xe2x80x2 may be possibly separated.
However, there are disadvantages in the above packed column type of vapor-liquid contactor in that a higher column should be provided and costs for the production and construction of an apparatus are high, when compared to the sieve tray column type of vapor-liquid contactor having the identical liquid and vapor loads. In this regard, it has been requested to develop a vapor-liquid contactor capable to increase a load, without occurring a flooding by increasing the upper limit of the liquid and vapor loads. It has been also requested to develop a vapor-liquid contactor enabling to vary the production rate in a broad range.
An object of the present invention is to eliminate the above-mentioned problems of the prior art and to provide a vapor-liquid contactor capable of increasing the load.
The inventors have conducted extensive experiments using a freon which is a liquid having a similar viscosity to a cryogenic material of air components such as nitrogen, oxygen and argon. As a result, the inventors have discovered that a low viscosity liquid of the above-mentioned cryogenic air component is easily dispersed on the surface of the packing such that a vapor-liquid contact of a high efficiency cab be therefore expected. Also, when a vapor-liquid contactor having a self-promoting-fluid-dispersion type structured packing is used, it is difficult to allow the liquid to flow in the downward surface (reverse surface) of the inclined part of the packing whereby a vapor-liquid contact efficiency becomes low. The present invention is made on the above discovery.
In the present invention, a vapor-liquid contactor is characterized by using a non-promoting-fluid-dispersion type structured packing in which various types of thin sheets or tubes for determining a flow direction of the liquid or vapor to the vertical direction are laminated and arranged to conform to the perpendicular direction, and including at least one fluid dispersion unit which comprises a rough distribution part to roughly distribute the liquid and a minute distribution part to minutely and equally distribute the liquid.
Further, the present invention is characterized in that the said non-promoting-fluid-dispersion type structured packing has a specific surface area more than 350 m2/m3.
Further, the present invention is characterized in that the minute distribution part to minutely and equally distribute the liquid is formed with a self-promoting-fluid-dispersion type structured packing.
Further, the present invention is characterized in that the minute distribution part to minutely and equally distribute said liquid is formed by laminating at least one non-promoting-fluid-dispersion type structured packing and parallel plane sheet group in the axial direction of the column, where the parallel plane sheet group may be a metal.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type structured packing is formed with a thin metal sheet group or a metal tube group. This thin metal sheet includes aluminum, aluminum alloy, copper, copper alloy, various stainless steel and the like, where a sheet metal net having more than 10 meshes is included.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type structured packing is formed with various kinds of plastic based thin sheet group or tube group.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type structured packing has a shape angled in a flow channel cross-sectional pattern. The angled shape includes various shapes of polygons and corrugations of a saw-tooth shape and the like.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type structured packing has a triangle shape in a flow channel cross-sectional pattern.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type structured packing has a quadrangular shape such as square, rectangular, trapezoid and rhombus in a flow channel cross-sectional pattern.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type structured packing is hexagonal in the said flow channel cross sectional pattern.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type packing comprises a wavy thin sheet formed of a curved surface.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type packing has more than two cross section patterns selected from the group consisting of a triangle, a quadrangle and a hexagon.
Further, the present invention is characterized in that said non-promoting-fluid-dispersion type structured packing comprises a plurality of thin sheets arranged by a spacer.
Further, the present invention is characterized in that said thin-sheet or spacer has at least one of corrugations, flutings, grooves, alternating-peaks-and-troughs, and/or holes.
Further, the present invention is characterized in that at least one vapor distributor for distributing the vapor is provided at the bottom of said non-promoting-fluid-dispersion type structured packing.
Further, the present invention is characterized in that said vapor distributor is formed with a self-promoting-fluid-dispersion type structured packing.
Further, the present invention is characterized in that said cryogenic air separation unit uses the said vapor-liquid contactor.
According to the present invention, there is provided a gas separation method, the method comprising the step of separating a vapor mixture component from at least two gas components mixture using a vapor-liquid contactor, the improvement being characterized in that said vapor-liquid contactor has a non-promoting-fluid-dispersion type structured packing formed of various types of thin-sheets or tubes to direct the flow of said mixture vertically, arranged in the direction perpendicular to the flow of said mixture; said non-promoting-fluid-dispersion type structured packing has a specific surface area of greater than 350 m2/m3; said vapor mixture and the cryogenic material thereof flow in countercurrent with respect to the surface of the packing under a pressure of from 0.08 to 0.4 MPa while performing vapor-liquid contact; and the loads of the vapor and liquid are so determined that superficial F factor is greater than 1.8 m/s(kg/m3)1/2.
Further, according to the present invention, there is provided another gas separation method, the method comprising the step of separating a vapor mixture from at least two gas components mixture using vapor-liquid contactor, the improvement is characterized in that said vapor-liquid contactor has a non-promoting-fluid-distribution type structured packing formed with various types of thin-sheets or tubes to direct the flow of said mixture vertically, arranged in the direction perpendicular to the flow of said mixture; said non-promoting-liquid-distribution type packing has a specific surface area of greater than 350 m2/m3; said vapor mixture and the cryogenic material thereof flow in countercurrent along the surface of the packing under a pressure of from 0.4 to 2.0 MPa, while performing vapor-liquid contact; and the loads of the vapor and liquid is so determined that a superficial F factor is greater than 1.0 m/s(kg/m3)1/2.
The vapor-liquid contactor according to the present invention uses as a packing a non-promoting-fluid dispersion type structured packing wherein thin sheets or tubes are laminated or arranged along the perpendicular direction in which various types of shapes for determining a flow direction of said liquid and vapor streams are formed over the perpendicular direction of thin sheet or tube. The vapor-liquid contactor includes at least one liquid distributor consisting of a rough distribution part to distribute the liquid roughly, and a minute distribution part to distribute the liquid minutely and equally. Accordingly, in the liquid distributor, the descending liquid is uniformly distributed over the whole cross-section of the column. Thereafter, in the non-promoting-fluid-distribution type structured packing wherein thin sheets or tubes formed in the perpendicular direction of flow streams are laminated or arranged in the perpendicular direction, a sufficient ascending vapor stream channel is assured by carrying out a vapor-liquid contact, a descending liquid in the surface of the packing is smoothly flowed and an uniformity of thin sheet is retained over the whole sections. The whole surfaces of the packing is effectively used. For this reason, an increase in the pressure loss due to an increase in a flow resistance of the ascending vapor can be reduced, a occurring of flooding can be prevented, a sufficient vapor-liquid contact area can be assured and an efficient distillation can be carried out. Accordingly, the load of the liquid and vapor can be established highly.
Further, the height of the column can be set lower. The costs required for the preparation and construction of the apparatus can be reduced. In addition, the product output can increased and reduced largely.